Apex sealing member for rotary piston engine

ABSTRACT

Herein disclosed is a three-layered apex sealing member for use with an internal combustion engine of rotary type. The apex sealing member is made of cast iron but composed of an upper portion having a chilled structure and formed with a sliding top surface for sliding engagement with the inner peripheral surface of the engine housing, of a lower portion having a chilled structure to be operatively received within the apex seal groove, and of an intermediate portion left unchilled and sandwitched between the upper and lower chilled portions. With these construction arrangement, thermally deforming forces to be exerted on the interfaces between each pair of the chilled and unchilled layers are oppositely directed and accordingly offset, so that an undesirable deformation of the sealing member is substantially eliminated.

United States Patent [191 Yamazaki Aug. 20, 1974 [75] Inventor: Ryuichi Yamazaki, Hiroshima,

Japan [73] Assignees: Toyo Kogyo Co., Ltd.; Yoshiwa Kugyo K K, both of Hiroshima-ken, Japan [22] Filed: Feb. 13, 1973 [21] Appl. No.: 332,084

[30] Foreign Application Priority Data Feb. 17, 1972 Japan 47-17461 [56] References Cited UNITED STATES PATENTS Gomada 418/178 3,672,798 6/1972 Scherenberg 418/113 Primary Examiner-Louis R. Prince Assistant Examiner-Robert 1. Smith Attorney, Agent, or Firm-Fleit, Gripple & Jacobson [5 7 ABSTRACT Herein disclosed is a three-layered apex sealing member for use with an internal combustion engine of rotary type. The apex sealing member is made of cast iron but composed of an upper portion having a chilled structure and formed with a sliding top surface for sliding engagement with the inner peripheral surface of the engine housing, of a lower portion having a chilled structure to be operatively received within the apex seal groove, and of an intermediate portion left unchilled and sandwitched between the upper and lower chilled portions. With these construction arrangement, thermally deforming forces to be exerted on the interfaces between each pair of the chilled and unchilled layers are oppositely directed and accordingly offset, so that an undesirable deformation of the sealing member is substantially eliminated.

3 Claims, 2 Drawing Figures APEX SEALING MEMBER FOR ROTARY PISTON ENGINE BACKGROUND OF THE INVENTION The present invention generally relates to an internal combustion engine of rotary type, and more particularly to an improvement in an apex sealing member for use with a rotor of the rotary piston engine.

A variety of constructions and materials have heretofore been proposed and developed for use as an apex sealing member of a rotary piston engine. It is well known in the art that such an apex sealing member is placed under remarkably severe working conditions. This is partly because the sealing member is directly exposed to the engine combustion gases at a high temperature, and partly because it is required to secure sufficient sealing effects even in the presence of a high pressure difference between the engine working chambers which are separated by its moving contact surface. One of the most successful proposals is a sealing member made of cast iron and having its upper portion with the contact surface chilled to acquire a sufficient hardness. The sealing member of this type has been practically appreciated at its prominent advantages including an excellent toughness and wear-resistivity (that is, resistivity to an extraordinal wearing which is often encountered in the rotary piston engine).

When, however, this sealing member is put into actual use in the combustion chamber working at a high temperature, it will easily suffer from heavy thermal deformation due to the considerable difference in the coefficients of thermal expansion between the chilled upper portion and the lower unchilled portion. This thermal deformation will lead to the longitudinal warping or bending of the sealing member with its longitudinal ends raised from the bottom of the apex seal groove, which is formed in each apex portion of the engine rotor. Accordingly, the so-called blow-by of the combustion gases through the depressed central portion of the apex sealing member occurs to invite deterioration of the sealing efficiency. As a result of this warping, moreover, only the raised end portions of the sealing member will be excessively pressed to result in the so-called fatigue rapture.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide an apex sealing member for use with a rotary piston engine.

Another object of the invention is to provide an apex sealing member made of cast iron, in which the undesirable thermal deformation is substantially eliminated without affecting the intrinsic tough property of the material.

Still another object is to provide an apex sealing member of cast iron, which is integrally composed of an upper portion having a chilled structure and formed with a sliding top surface for sliding engagement with the inner peripheral surface of the engine housing of the rotary piston engine, of a lower portion having a chilled structure to be received within an apex seal groove, and of an intermediate portion left unchilled and sandwitched between the upper and lower portions.

In accordance with the present invention, the apex sealing member has a three-layered structure in which an unchilled tough cast iron layer is integrally interposed between upper and lower chilled hard layers. Thus, there are formed two interfaces between each pair of the chilled and unchilled layers, and as such the thermally deforming forces to be exerted on the interfaces are oppositely directed and accordingly offset, to thereby eliminate the undesirable longitudinal warping.

BRIEF DESCRIPTION OF THE DRAWING Other objects and advantages of the present invention will be described with reference to the accompanying drawing, in which:

FIG. 1 is a perspective view showing an apex sealing member according to the present invention; and

FIG. 2 is an explanatory view illustrating the method for comparatively gauging the thermal deformations of the present and conventional apex sealing members.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, an apex sealing member according to the present invention is generally indicated at reference numeral 10. The sealing member 10 is made of cast iron comprising, as shown, an intermediate portion ll, an upper portion 12 and a lower portion 13. A detailed discussion on the method of manufacturing and chilling one surface of an apex sealing member appears in US. Patent 3,658,451, and accordingly merely a short description will be given of the present method of manufacture. The present sealing member 10 is manufactured, for instance, from an elongated body made of acicular cast iron, which is composed by weight of 3.6 percent of carbon, 2.1 percent of silicon, 0.4 percent of manganese, 0.5 percent of chromium, 1.5 percent of molybdenum, 1.0 percent of copper, and the balance is iron. The lower portion 13 and the upper portion 12 formed with a sliding contact surface are locally molten within a short time period by the use of either of the electron beam, plasma or laser beam method in a manner to leave the intermediate portion 11 unchilled. Then, the elongated body with the locally molten portions is quickly cooled down as a whole to obtain the chilled structures at the upper and lower portions 12 and 13. In an alternative, the melting and chilling step may be, if desired, performed separately on the upper and lower portions. Then, the locally chilled body is subjected to machining to be fittedly received in the apex seal groove.

The apex sealing member thus obtained has, for example, such dimensions as the length a of mm, the height b of 8.5 mm, and the width 0 of 5 mm, as shown. And, the thickness or height t, of the upper chilled layer 12 is about 2.5 mm, but the thickness t of the lower chilled layer 13 is, preferably, slightly less than 2.5 mm, thus leaving the unchilled layer 11 of about 3.5 mm. In this way, it is preferable for the practicaly purposes that the upper chilled layer 12 has a larger thickness than that of the lower chilled layer 13. This is easily reflected by the fact that in operation the upper portion of the apex sealing member is exposed directly to the hot combustion gases to thereby have a steep negative temperature gradient toward the remaining portion which is received in the apex seal groove. And, the upper portion is formed with the sliding top surface which is in moving contact with the inner peripheral surface of the engine housing of the rotary piston engine, so that its thickness will be progressively worn out in the cource of operation. If, therefore,- there exists the steeper temperature gradient across an interface between two materials having different coefficients of thermal expansion, it is well known in the art that the interface will warp the more. From these reasonings, the upper interface between the chilled and unchilled layers 12 and 13 should preferably be positioned not above the outer edges of the apex seal groove but in the particular groove where the temperature gradient is more gentle. This positioning will practically be exemplified by the above thickness relationship that the upper chilled layer 12 has a larger thickness than that of the lower chilled layer 13.

In order not to adversely affect toughness of the present apex sealing member as a whole, on the other hand, it is empirically found that the thickness of the intermediate unchilled layer 11 should be at least one-fifth of that of the whole sealing member 10. The thickness control of these three layers can be carried out by selecting appropriate values of the energy level, energy density and scanning speed of the electron beam as used.

Turning now to FIG. 2, comparison of the thermal deformation characteristics will be made between the present apex sealing member having its upper and lower portions chilled and the current apex sealing member having only its upper portion chilled. The measuring system is, as shown, of common type, in which either of the apex sealing members is horizontally supported at two supports 14 and 15 spaced from each other at a distance of about 50 mm. A dial gauge 16 is disposed at the opposite halfway of the two supports 14 and 15 so as to gauge the thermal deformation of the apex sealing member in terms of the displacement of the halfway portion with respect to its ends. The measurements were made at an atmospheric temperature of about 15C and at an elevated temperature of 300C. The resultant thermal deformations will be tabulated in the following:

Present Sealing Member 500p. 495p. 5p. Current Sealing Member 5951.4 580;: l5p.

As apparent from the above Table, the present seal- 1 ing member far less suffers from the thermal deformation, and it can be said that the deformation value 5,LL of the present invention will never involve practical difficulties.

As has been described hereinbefore, the apex sealing member according to the present invention will experience highly reduced thermal deformation even when it is exposed to the hot combustion gases. As a result, the present sealing member is free over a prolonged period of operation time from the undesirable blow-by, pitching phenomena, thus improving the durability of its sealing effects. Moreover, the power performance of the rotary piston engine employing the present sealing member is highly augmented, because the improved sealing effects leads to increase in the obtainable compression ratio of the engine.

What is claimed is:

1. An apex sealing member for use with a rotary piston engine, comprising an elongated body of cast iron to be operatively received within an apex seal groove which is formed in each apex portion of a multi-lobed rotor of the engine, said elongated body including an upper portion having a chilled structure and formed with a sliding top surface for sliding engagement with the inner peripheral surface of the engine housing, a lower portion having a chilled structure to be received within the apex seal groove, and an intermediate portion left unchilled and sandwiched between said upper and lower portions.

2. An apex sealing member according to claim 1, wherein the thickness of said upper portion is larger than that of said lower portion.

3. An apex sealing member according to claim 1, wherein the thickness of said intermediate portion is at least one-fifth of the whole thickness of said elongated body. 

1. An apex sealing member for use with a rotary piston engine, comprising an elongated body of cast iron to be operatively received within an apex seal groove which is formed in each apex portion of a multi-lobed rotor of the engine, said elongated body including an upper portion having a chilled structure and formed with a sliding top surface for sliding engagement with the inner peripheral surface of the engine housing, a lower portion having a chilled structure to be received within the apex seal groove, and an intermediate portion left unchilled and sandwiched between said upper and lower portions.
 2. An apex sealing member according to claim 1, wherein the thickness of said upper portion is larger than that of said lower portion.
 3. An apex sealing member according to claim 1, wherein the thickness of said intermediate portion is at least one-fifth of the whole thickness of said elongated body. 